Mostly, it reminded me of a problem from wave mechanics my sophomore year in college. The question asked how far you had to stand back from a pointillist painting (of which I was now staring at the quintessential one), before the dots blended together to form a single tone. It was simple physics caused of diffraction through your pupil hitting the back of your eye.

This reminded me of how the the cells in the eye are just a big digital->analog processor, how processing is done in the eye to encode this in a small enough space to send down our optic nerve, and how understanding that and Nyquist Sampling allowed Hubel and Wiesel to win a Nobel Prize for explaining what our primary visual cortex does. In other words, the basics of what we see and why.

What’s weird about all this is how the biology and the physics/math agree. You can measure your own acuity and compare it to the Nyquist-Shanon Sampling Theorem. You can predict how the convolution should be and see it measure it electrically in the back of your cortex.

The question of when to buy a digital camera became simply a physics/math problem for me: at what point do the dots in the digital sensor become indistinguishable from a analog print of the highest resolution viewed at one foot.

The answer to that question has always been with us. It is what creates our hyperfocal distance and depth of field tables.

The answer was when the viewing distance is one foot, you needed 300dpi of resolution before Nyquist says that the dots merge together in our eye so as to not be dots at all—it was Seurat to the extreme. A 5″ print? you needed 2 megapixels. A 10″ print? 6 megapixel.

My C-2500L? 2.5 megapixel. My D70? 6 megapixel.

Here is something for you. 35mm film came to the photography world from cinema. At first it was deemed too grainy for serious photography, but chemistry kept improving. By the end of the film era, nature photographers (always a sticker for quality) were shooting most 35mm on Fuji Velvia 100.1 The size of the grains? The same as the size of a photosite in a D70 sensor.

That can’t be a coincidence, can it?

1 If you read the linked article, you will see that it claims that Fuji Velvia has 12 megapixels of image data not 6. That is correct, in fact it’s probably more than 12 by a measure of pure acuity. The difference is that pesky Nyquist sampling theorem which forces you (if you sample at regular intervals like a digital camera) to sample at twice the spatial frequency of the object you are resolving. This is why arguments like: which is better film or digital never seem to end. Tests like acuity are highly biased toward analog media like film with randomly distributed grain. There are other compromises due to film grain (besides the “slow” ISO 100) relative to digital that are obvious when you look at these things blown up.

Published by

tychay

8 thoughts on “When did you go digital?”

This article reminds me of how we also “trick” the brain in cinema. Basically, we’re throwing up images so fast that our brain perceives it as motion.

IMDB has a nice, straightforward explanation of this. It’s interesting to note that 24fps was selected as the cinematic standard because it’s about as low a framerate you can go and still fool the brain.

I use both digital and film cameras all the time. They each serve a different purpose.

Film and digital capture are completely different media. They are used for similar purposes, but they themselves are completely unrelated to each other. I’d have an easier time and get in less trouble comparing my mom to a maid or my wife to something else than attempting a comparison of film to digital cameras. That said, here goes.

Most people get better results with digital cameras. I prefer the look of film. Film takes much more work. Extremely skilled photographers can get better results on film if they can complete the many more steps from shot to print all perfectly. Because there are so many ways things can go wrong with making prints from film, especially from print (negative) film, beginning photographers and hobbyists usually get better prints from digital because there are fewer variables to control.

I get my digital prints made at Costco and they look stunning. Mark the Costco bag “Print as-is. No corrections” and your prints will look like your screen, so long as you’ve left your camera in its default sRGB mode.

Labs usually make awful prints from film, which is why people who don’t print their work personally get better results from digital. I’ve never been happy with prints from negatives made for me by any lab regardless of cost. This is because prints from negatives are at the mercy of the eye of the person making the print. If you’re not making the prints yourself you usually get something completely different than you wanted, which means junk. That’s why most photographers shoot slide (transparency) film, since the printer can see exactly what the photographer intended.

Large format film still rules for serious landscape photography.

I use digital for people, fun shots and convenience. Digital replaced film in 1999 for big-city newspapers.

The biggest reason the results look different is the highlights. We’re used to the way film looks. It overloads gracefully when things get too light or wash out. This mimics our eye far better than digital. Digital’s weak point is that highlights abruptly clip and look horrible as soon as anything hits white. Unlike film there is no gradual overload to white. Digital cameras’ characteristic curve heads straight to 255 white and just crashes into the wall. it’s the same with video versus motion picture film. If any broad area like a forehead is overexposed your image looks like crap on digital. This effect is similar on cheap pocket cameras, my expensive Nikon D200 and $250,000 professional digital cinema cameras.

A smaller reason is that film, especially larger format film used in landscape photography, has more resolution. This becomes important as print size increases to wall size but invisible in 5 x 7″ prints.